DS90UB913A-CXEVM: DLW21SN261XQ2 Choke ever used and tested?

Brian Antheunisse

Hi champs,

in the DS90UBUB913/4A EVMs, there are a series of coupled inductors (DLW21SN261XQ2) that all show as DNP. Can you explain why they were included, and if the design was ever tested with them populated? If so, I assume that the through path would go through the device and the trace would have to be cut. Can you verify this?

My customer is trying to figure out how to lower their EMI emissions, and they are considering this choke.

Thanks,

Brian

over 8 years ago

0 Ankur Verma over 8 years ago

TI__Intellectual 1500 points

Hi Brian,

Yes, the DLW21SN261XQ2 were added to the EVMs to help mitigate the common mode noise, however, these components are not populated on the board. Make sure when you add these components, the impedance discontinuities are minimized to avoid causing any reflections on the line. We don't have any testing data available to share with you, but please let us know if you face any further issues.

0 Brian Antheunisse over 8 years ago in reply to Ankur Verma

TI__Expert 5305 points

Ankur,

Are they just dropped in and work (to the EVM)? or does the trace need to be cut?

Thanks,
Brian

0 Liam Keese over 8 years ago in reply to Brian Antheunisse

TI__Genius 12705 points

Hello Brian,

Typically we only see CMC used when the system is configured for differential signalling. For coax this is not a common use case. For differential operation you would need to configure the boards for differential Rin+/- Dout +/-

0 Brian Antheunisse over 8 years ago in reply to Liam Keese

TI__Expert 5305 points

Ok, so in this use case, the CMC wouldnt improve EMI performance on a coax. Any EMI problems they are seeing are likely from Differential mode noise, so I should recommend the customer to either:

-use the choke (without the need to cut any trace or anything, just drop it in), and configure the boards for differential Rin+/- Dout +/-
or
-seek alternate methods of EMI mitigation.

Thanks,
Brian

0 Liam Keese over 8 years ago in reply to Brian Antheunisse

TI__Genius 12705 points

Correct. If they can identify the source of the EMI then appropriate countermeasures can be implemented.

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DS90UB913A-CXEVM: DLW21SN261XQ2 Choke ever used and tested?